It is desirable to have printers such as thermal printers in which it is easy to accurately load the dye donor ribbon. It is further desirable to make the printer as easy to use as practical while being cost effective in the manufacturing process. Some thermal printers have a disposable dye donor cartridge mounted in the printer to hold the dye donor supply and take-up spools and offer convenience of use because it is relatively easy to insert and remove the cartridge. This is especially true in instances where the cartridge is keyed, sized, or shaped to be insertable with only one orientation. While cartridges offer convenience, they are expensive and in some cases the cartridges are discarded after one use. Unfortunately, attempts to make cartridges reusable to conserve resources have failed because it is difficult to rewind dye donor in a cartridge at the point of use.
To eliminate the problems associated with cartridges, some printers have configurations that mount the donor spools in the print engine without the benefit of a cartridge, while other printers mount the spool in the printer door, again without cartridges. Where spools are used without cartridges, there are also problems that arise. Space is always a consideration and there is not always sufficient room for all hands to manipulate the spools, regardless of whether the spools are full or empty. A spool can be mispositioned on the drive elements and therefore completely inoperative, or may cause annoying printing errors.
Failure to correctly orient the supply and take-up spools creates a situation wherein the printer will not function properly, if at all. Correct loading requires having the supply and take-up spools in their proper places as well as having the donor supply spool oriented correctly end for end. Incorrect end for end orientation causes the web to traverse an incorrect path through the printer, if it traverses a path at all. With an improperly loaded dye donor web, it is very difficult, if not impossible, to achieve exact color registration and produce a quality image without undesirable artifacts.
While a careful and skillful operator can study the spools and the spool receiving mechanism and achieve correct insertion of the supply and take-up spools, doing so is burdensome, even for a skilled operator. An operator does not want to read lengthy or complicated instructions or observe burdensome or annoying practices just to ready a machine for use, and typically has more than one machine to operate and desires convenience so that having to refer to manuals or read instructions is quite a burden. An operator wants to simply drop the donor web into place, especially where doing so is an occasional and unscheduled chore. Accordingly, it will be appreciated that it would be highly desirable to have an apparatus and method for simply and correctly loading a donor web wound upon a spool into the printer which prevents operation of the printer when incorrectly loaded.
Accordingly, commonly assigned U.S. Pat. No. 5,513,920 filed on Oct. 29, 1992 by Whritenor et al. describes a thermal printer apparatus comprising a supply spool having opposed cylindrical ends of substantially the same diameter and shape and a pair of spaced, rotatable, axially aligned spindles adapted to receive a respective one of said opposed ends of said supply spool, there being a correct end-for-end orientation of said supply spool and an incorrect end-for-end orientation of said supply spool on the spindles. The printer has a mechanical stop member in the space between said spindles and closer to one of the spindles than the other. A dye donor web to be used in the printer is wound on said supply spool to form a cylindrical roll which is axially shorter than said spool and axially off center of said spool so as to leave a substantially longer portion of the spool extending beyond one end of the roll than extends beyond the other end of the roll, whereby the roll will interfere with the mechanical stop member of a thermal printer of the type described when an attempt is made to insert the apparatus incorrectly in such a thermal printer, but will not interfere with the mechanical stop member of a thermal printer of the type described when an attempt is made to insert the apparatus correctly in such a thermal printer.
The '920 patent also describes a variety of other modifications that can be made to a web spool that can be used to help ensure that donor or receiver web spools are properly loaded into a printer media supply including but not limited to the use of differently sized donor and take up spools, donor and take up spools with differently shaped or sized ends, donor and take up spools of different length, and donor and/or take up spools having ends that are different.
Such mechanical solutions, while commercially viable and highly useful, requires that all media that is inserted into a printer that is so adapted conform to the requirements that are set by the manufacturer of such a printer. However, not all manufacturers agree upon such standards and therefore many makers of media provide media on spools that are adapted to be compatible only with a limited number of manufacturer's products or incur additional costs in providing a wide variety of different media types on different spools.
Another solution followed in many printers to prevent mis-loading is to apply a machine readable marking or indicator on the spools, a memory chip, or a wireless memory chip such as a Radio Frequency Identification transponder that can be read only when the spool is properly loaded. This solution, while also highly useful and valuable further increases media manufacturer costs in that the media manufacturer must not only provide mediums that are adapted to conform to the spool geometry and media geometry but must also provide an appropriate set of markings, properly programmed memory chips, or properly programmed RFID transponders, and must position such markings so that they can be detected properly.
What is desired therefore is a new approach to providing media supplies that allows a consumer to use a non-specific media in a printing device that is adapted to receive media of a specific type.